SINGAPORE - A 14-year-old boy coaxed his stepsister into the bathroom of their home and forced the then five-year-old to perform oral sex on him.

The incident happened some time between June and September 2017, a district court heard on Wednesday (Jan 29).

Now aged 17, he has pleaded guilty to one count of sexually penetrating the girl without her consent. He cannot be named because of a court-imposed gag order to protect the girl's identity.

Deputy Public Prosecutor Sean Teh said the boy was watching pornography on his mobile phone in the bathroom when the girl opened its door and saw him masturbating.

The DPP told District Judge Seah Chi-Ling: "The accused reached for the victim's hand as he was still sitting on the toilet bowl, and coaxed her to enter the toilet. The victim initially refused."

He grabbed her hand and promised to give her chocolate if she performed oral sex on him.

He sexually penetrated the girl without her consent and she ran out about 10 seconds later when he released his grip on her.

On Feb 4 last year, she was referred to the Marine Parade Family Service Centre (FSC). Court documents did not disclose the reason.

During a counselling session at the FSC, she said her stepbrother had sexually penetrated her.

The Ministry of Social and Family Development was alerted on March 8 last year and a child protection officer made a police report the same day.

The youth, who was unrepresented, told the court he was sorry for what he had done, adding: "I intend to continue studying and have a brighter future."

Judge Seah has called for reports to assess his suitability for both probation and reformative training.

Offenders given reformative training will be detained at a centre where they will follow a strict regimen that includes foot drills and counselling.

The teenager will be sentenced on Feb 5.

Offenders convicted of sexually penetrating a minor younger than 14 without consent can be jailed between eight and 20 years and receive at least 12 strokes of the cane.